A multidisciplinary aaproach is used to assess the functional state of normal and diseased human intercostal muscle in-vitro. Membrane excitability, pharmacology and morphology of muscle fibers are examined. The working hypothesis of this project is concerned with the neurogenic cause of muscle disease. By direct comparison of human and animal muscles, under similar conditions, we are attempting to ffnd similarities or differences between surgical denervation and muscle dysfunction. This has already resulted in data indicating that myotonia may be neurogenic whereas Duchenne dystrophy probably is not. In addition we are examinining the existence of a self feedback loop from the muscle into itself as evidenced by normalization, consequent to electrical stimulation, of muscle functions which are altered by denervation. Finally, we are expanding our work on steroid-induced myopathy to the examination of neuromuscular transmission by measuring end-plate and miniature endplate potentials.